Noise exposure is a major cause of hearing loss worldwide. Following noise exposure, damage to diverse structures in the cochlea are seen, including the spiral ganglia nerve fibers that normally form synaptic contacts with hair cells in the cochlea. These synapses enable the spiral ganglia to convey acoustic information from the cochlea to higher order structures in the brain stem. Following noise exposure, hair cells release neurotransmitters that lead to excitotoxic damage in the neurites, resulting in synaptic disruption and neurite retraction (Kujawa, S. G. et al., J. Neuroscience, 29, 14077-14085 (2009); Lin, H. W. et al., Journal of the Association for Research in Otolaryngology, 12, 605-616 (2011); Spoendlin, H., Acta Oto-Laryngologica, 79, 266-275 (1975)). Following moderate noise exposure and neurite refraction, some neurite regeneration can be seen, which restores synaptic connectivity and auditory capacity (Puel, J. L. et al., Neuroreport, 9, 2109-2114 (1998)). However, persistent noise exposure or intense acoustic trauma can result in permanent neurite degeneration.
Thus, there remains a need for new methods for preventing and/or treating noise-induced hearing loss.